In the Heart of Darkness
by cosmicam
Summary: This is an Underfell fanfic. NSFW will come eventually, I'm not sure how explicit it will be but it will be tagged the heck out of. Sans/Reader. Abuse/Abandonment/Depression are some of the heavier themes here.
1. Chapter 1

You woke up on yellow flowers.

They almost glowed in the blackness of the cavern. You pushed yourself up, but a sharp pang in your chest brought you back down on your face. A small whimper escaped you as you buried your head in the velvety petals. After most of the pain has subsided to an ache, you flipped yourself around to face up.

Taking deep breaths, each one straining your bruised chest, you tried to think straight. You had fallen down, and somehow not died. This didn't make any sense. Far above you, the stars twinkled faintly. Moonlight filtered down through the hole, to be reflected on the golden petals surrounding you.

What was this?

Your second attempt to get up was painful, but successful. Rubbing your eyes, you adjusted to the gloom of the cave. There was an opening, just down a little farther.

You hobbled your way towards the dull light of the opening, wondering why there was light down here at all. Stepping into another cavern type place, you noticed a small piece of dirt lit by a faint ray of moonlight. There was a flower there, like the ones you had fallen onto, but a little bigger.

You approached the flower. It seemed to be…

"Huh? W-who are you?" The flower said.

You stepped back, mouth gaping. Did the flower just…

"Oh no… You're human aren't you?" The flower's face, _it had a face,_ took on an expression of concern.

"W-what?" you breathed, nearly inaudible.

"Look, you've got to get out of here. You don't understand what they'll do to you…"

The flower looked up at you alarmed, but then paused, confusion crossing its face.

"Hey, are you okay?"

You took another deep breath, and tried to find words.

"W-what's going on?" you asked, trying to keep your voice smooth. "Where am I?" _Why am I talking to a flower?_

"You're in the Underground. Don't you know about this place?" The flower inquired, its eyebrows knitted.

You shook your head.

"Geez, you've got a lot to catch up on."

"So, why are you here?" you asked the flower, fiddling with your bootlace.

Flowey, the flower also had a name, had filled you in on the barrier, the monsters and their not so friendly opinion of humans. It was all... too much to take in. But you didn't feel like you had a choice. You could contemplate reality later.

"I had nowhere else to go." he said, looking away. "I'm not exactly a celebrity back there, and there's no way I could get through the barrier. I've been for a long time, warning each human that has fallen down."

You stared down at the ground, only able to imagine what he had gone through to try to save the six that had come before you.

"I could take you with me." you offered.

It was possible that you were trusting him too much, for being the only thing you had actually met down here, but you really didn't feel like he was lying to you. You felt like you needed to protect him.

He looked at you for a second, mouth parted. This had never occurred to him.

"Really?" The flower shook his head, looking down again. "No, that's… that's too dangerous. You can't carry me around, I'd slow you down. You have to get out of this place as fast as you can."

You thought for a second, ignoring his words, then started unlacing your left boot.

"Would you mind if I…?" you gestured to your boot.

Flowey stared at you, and for a second you thought you had offended him.

"Well… I guess that could work." He looked at the boot. "But I'm still going to weigh you down, Y/N."

"You're a _flower._ And besides, I'll need help navigating, right?."

 _And I don't want to lose the only trust I have down here._

You smiled at the flower, taking a handful of loose soil and packing it into the boot. Flowey watched as you carefully dug around his roots, and lifted him.

"There you go." You pushed the dirt in firmly.

Standing up, you picked up the boot and tied the laces securely around your neck. You laughed. This actually worked well. You made sure Flowey was comfortable, and headed down into the tunnel.

You two eventually found yourselves in a lit corridor. Vines crawled over the dark pink walls, emitting an odd air that unsettled you.

"These are the Ruins, Y/N… They're mostly deserted, we just need to be careful."

You nodded and nervously continued down the path. Flowey had told you about the monsters, but it was always different coming face to face with something.

Which is what you did as you rounded the next corner.

The frog-like thing hopped back a step when you nearly collided with it, but then, realizing what you were, jumped at you. You barely dodged, spinning around to face the monster. You put your hands up in a passive signal.

 _I'm not going to hurt you, damn it._

You could've sworn the frog stopped and looked at you funny. Its next leap was easier to miss, now that you knew it was coming. After a couple rounds of this, with Flowey yelling at you to dodge, you were beginning to tire.

 _This thing is relentless._

Just as it was about to attack again, a fiery orb knocked it aside. You jumped back, watching the frog quickly hop out of sight. Spinning towards the source of the fire, you found a woman… with goat ears?

Looking closer, it wasn't just her ears. She was some sort of humanoid goat, wearing a dark purple robe.

"Oh, how dreadful! Poor children…" the goat woman rushed towards you, clasping two furry paws together.

"Are you okay? That terrible creature did not hurt you did he?"

You backed away from her, taken back by her gleaming, yellow eyes.

The goat woman stared at the two of you in a tense silence, eyes flickering down to Flowey, and then to your missing boot.

"Oh! We must get you new shoes, my darling. You cannot very well run in those can you?"

You didn't respond. It was true being half shoeless was a pain, but you were getting a strange feeling from this woman.

She took your hand with one soft, furry paw and placed the other on your cheek.

"Let us get you both somewhere safe. It is dangerous out here for two helpless children such as yourselves." The goat woman smiled again, dark eyes gleaming.


	2. Chapter 2

Her house was in good condition, almost like it had been preserved. Flowey had been oddly quiet since you encountered Toriel. She had taken you through trap after trap, stressing just how lethal each one was. As she explained, she had kept a close eye on your reactions and an ever-tightening grip on your hand.

Now you stood in the main entrance of a fairly welcoming home. There was a strong scent of cinnamon in the air.

"Now, let me show you your room, young ones."

 _Our room? Just how long does she expect us to stay here? And why did she seem so… prepared?_

Toriel took a step towards the hall, but suddenly stopped and turned around.

"Why, I have forgotten to ask you your names!" She placed her large paws on your shoulders. "I do apologize! But it feels as if I already know you both."

"My name is Y/N." you mutter quietly.

Flowey took a moment, warily glancing at Toriel before looking away. "I'm Flowey."

Toriel smiled. "Such lovely names for such innocent children."

With that, she continued down the hall, stopping at the first door on the left.

"I do hope you will be happy here. You should both rest for now. I have a cinnamon-butterscotch pie in the oven that we will share later."

Toriel patted your head, and lightly brushed Flowey's petals. He moved away slightly at the touch. The goat woman gave another sickly-sweet smile and hurried off to the kitchen.

You tentatively opened the bedroom door. It was a child's bedroom. It looked like everything had been set in place, like a museum. It felt staged. As you looked around the room, you were filled with a great sense of despair, This woman had lost someone. A child.

As uncomfortable as you were, you could feel exhaustion creeping into your mind. It would probably be best to take this opportunity to sleep. You untied Flowey's boot from your neck, and set him on a bookcase.

"Are you alright?" you asked him.

Flowey looked at you with sad eyes, but replied "Yeah, I'll be fine."

You decided not to push it right now. "I'm going to nap for just a bit. Wake me up if anything happens."

Flowey nodded sullenly.

You woke up on yellow flowers.

You stood. The cavern was pitch black. You couldn't see the tunnel you had gone through to find Flowey, or the hole in the mountain that you had fallen down. You couldn't even see an inch in front of you.

Moving slowly, you stumbled through the darkness with your hands reaching out. Suddenly, you felt something brush against your fingers. It felt like cloth. You gasped and pulled back, but then cautiously reached out again to grasp the material. It was thick, fitting in both your palms as you ran your hands up, trying to figure out what it was. Realization dawned on you as your fingers found a zipper. Before you could take your hands back, you felt a strong grip around both of your wrists. You looked down, and panic rose as you found two skeletal hands locked around you.

You let out a cry of protest, trying to wrench your hands free. Your captor moved suddenly, a flash of red crossing your sight before you found yourself held against their solid frame, wrists now held by one hand behind you. Panic rose as you tried to break free, unsuccessfully.

"You shouldn't have come back." a deep, voice growled against your neck.

Your breath caught short as you felt a iron-hot pressure close around your throat. You felt your feet leave the ground, your back grinding up against the skeleton's chest. Kicking your feet violently, you struggled for a last breath…

"Y/N! Y/N wake up!"

You jolted up off the bed. Sweat ran down your face as you gasped for oxygen. You locked eyes with Flowey, who had been screaming at you from the bookshelf. You ran your hands through your hair, gulping.

 _Who was that?_

"What was that? Are you okay?" Flowey questioned you.

"I- I don't know." you breathed. "Th-there was a skeleton… killing me…"

You turned to Flowey, an expression of fear on his face.

"What?" you asked.

He looked away from you, and you got up.

"Flowey, do you know who I'm talking about?"

Meeting your eyes again, Flowey answered.

"Yes… I know him."


	3. Chapter 3

You stared at Flowey, waiting for an explanation.

"Was there… red?" Flowey asked you quietly.

You nodded, eyebrows furrowed. You weren't angry, you were scared. The Underground was proving to be more hostile than you had thought.

"Yeah." Flowey breathed. "That was… Sans. I've fought him before. Or tried to at least. I could never make a dent on him. He made me reset more than anyone else ever could."

You had almost forgotten Flowey once had the power to reset.

"You were fighting him?" you asked, confused. Flowey hadn't mentioned anything about fighting anyone before. Now that you thought about, you didn't really know all that much about him.

"I… back there, I didn't tell you everything. Before I came to the Ruins, I was different. I wasn't a flower. I was prince Asriel."

You were even more confused now. You knew about the King, Asgore. But this whole Prince Asriel to Flowey thing wasn't adding up.

Flowey looked at you. "It's a little complicated. But anyways… I lived in the castle with my parents. One day, I found a human. Like you, she had fallen from the Surface. Her name was Chara."

Flowey's voice grew quiet and seemed full of something you couldn't place.

"We took her in. Me, Asgore and… Toriel. Toriel was the queen, my mother."

Your mouth opened, but you quickly closed it. It made sense now, why Flowey had been so quiet since Toriel had found you. You assumed she didn't know who he truly was.

"Anyway. Me and Chara grew up to be best friends, but one day she got sick. She… she wanted to return to the Surface. To see the flowers. But we couldn't cross the Barrier. She died under the mountain."

Flowey's voice was shaking, and he was turned away from you.

"When she died, I fused with her soul, and carried her body through the barrier. I took her to the village, and laid her in the flowers. You should've… seen it, Y/N."

You stared at the floor, silent.

"But the villagers found me, kneeling over her. They attacked, and I couldn't hold off. I took her back, through the barrier. I made it to the garden… where I died. My soul scattered across the flowers there, and fused again so.." he trailed off, looking down at the soil he was rooted in.

"My parents" he continued. "fell into grief. My father declared war on the Surface. But my mother left. She couldn't hate humans after Chara. But I hid from them, from everyone once I took this form, and started wandering the Underground."

"I saw them all change. They all started to hate the humans. But there was one in Snowdin who was… slower, I guess. Slower to hate. I approached him in the forest one day. I'm not sure what I wanted. I thought maybe if I could change one person's mind, I would have done something."

"He was reluctant at first, insisting that he hated the humans more than anyone else, but I came to know him. He was a good person, Papyrus. We talked in the forest almost everyday from then on, and I began to really believe I could change all their minds."

Flowey turned back and looked at you.

"That's when his brother found me. I was waiting for Papyrus one day as usual, but I came face to face with Sans instead. 'So you're the weed that's been sweet-talking my brother, huh?'" Flowey mimicked. "And from there… it just gets bloody." Flowey shook his head.

A shiver ran up your arms.

"I reset over and over again, until he finally let me go. Before he did though, he told me to remember something."

You looked up at Flowey, who was staring you dead in the eyes.

"' _ **e, i t ' d.**_ '"

You tensed. The words had taken on a dark, dual tone resounding in your head. You'd heard them before.

 _From the dream..._

"So… that's Sans." Flowey stated dispassionately. "I'm sorry to scare you like that. You just need to know-"

"I'm alright." you assured him, lying through your teeth a little too quickly.

Standing up and stretching your legs, you gave Flowey a smile. You had a feeling he knew you were making an effort.

"But, Flowey… I am sorry about Chara." you offered. And you were.

It was his turn to give you a smile. "Don't worry about it. We're friends now, right?"

You nodded and really smiled that time.

"Well…" you continued after a brief silence, "are we ready to go, then?"

Flowey met your eyes and nodded. "She's going to be hard to get through, Y/N. She won't let you go easily."

You secured Flowey around your neck, and stepped into the hall. The smell of cinnamon was even stronger.

"I know." you said softly.

Toriel was in the kitchen. She turned to face you and Flowey, pulling a pie out of the oven.

"Oh! Already up? Did you sleep well, my child"

You nodded. Again with the lying.

Toriel smiled sweetly at you, then turned to slice the pie.

"So," she said, "I have been preparing a curriculum for your educations. I've always wanted to be a teacher, to tell the truth."

Your heart sank. This was going to be hard.

"Toriel," you said quietly, "We can't stay here."

You stopped there, and the silence grew.

"Oh, my child," Toriel responded, a little mellower, "You don't have to be so formal with me. You could call me 'Tori', or even… 'mother', if you wanted to."

You stomach turned. Not out of disgust, but out of sadness. But you held fast. Flowey deserved to get to the Surface, and you couldn't give up on him.

"I need to get back to the surface." you continued, watching her reaction. That was a lie, too. You had no intention of going back.

She stood still for a moment, holding a plate up to the pie.

"Excuse me, children." She set the plate down. "I have something I need to do."

Toriel hurried out of the kitchen, and you followed. She disappeared down the stairs. Walking carefully, you found her at the end of the long hallway.

"Don't try to stop me, my child. You don't know what they'll do to you." Toriel's voice was dangerously low.

 _I'm getting tired of people telling me that._

She continued towards a light at the end of the corridor, pausing before it as you caught up to her again.

"He'll kill you both." Toriel turned, grinning widely, yellow eyes flaring. "He promised he would, if I couldn't."

You were scared now.

"Who did?" you whispered, though you felt you already knew the answer.

Toriel laughed. "It doesn't matter. You won't be leaving, my children. I'll drag you back if I have to."

With that, she conjured a fiery orb in her palm, and launched it towards you. You dodged as quickly as you could, smelling the singed fabric of your shirt's hem. You stood your ground and looked at Toriel, who grinned back.

"You won't fight back? My child, how do you suppose you'll survive out there? Don't you realize? Down here it's _**kill or be killed.**_ "

You clenched your jaw.

Toriel's laughter filled the room as you desperately maneuvered through a new barrage of fire. The orbs came in waves, but you never raised a hand against her. But it was getting harder and harder to get away unscathed. You were tiring quickly, already having earned more than a few burns over your body.

"I'm sorry, Toriel." you panted, "We have to keep going... "

She didn't falter. Another set of flames came at you.

"I know they all say the same thing." you tried. Toriel glanced at you curiously, the next orbs slowing a bit.

You pressed on. "The other humans. I'm sorry you had to see them all leave." you looked up at her, and she had froze altogether, her face shadowed. The corridor fell quiet.

"I'm sorry you lost them."

Then there were tears running down her face, falling to the floor. The flickering orbs of fire in her hands cackled, forgotten. She didn't make a sound.

"They never understand." Toriel finally said. "...They never realize what happens beyond this door. They don't know how many have died." Her paws clenched, and she shook.

"You'll be _eaten_ alive! Can't you see?" Tears flew as Toriel spat the words at you, her yellow eyes desperate. "Do you want that? Your soul… removed? Torn? I've seen it happen-" a choked cry escaped her. "-six times before."

Toriel quieted again, her shoulders racking with sobs. You stood with your fists clenched, feeling horrible that you had brought her to this. Flowey was still.

Then, slowly, you stepped forward. You wrapped your arms around Toriel and for a second, she didn't move. But then you felt her paws on your back, pulling you in tightly. She pressed her head against yours and rocked you slowly. You closed your eyes.

"My child." she said shakily.

Toriel held you both for a long time. You wanted to say something, anything, to show her she deserved love. But before you could, Toriel stood up. She started to say something, her eyes on the floor, but seemed to change her mind and whispered quietly,

"Be good, won't you?"

And she left.

You stood in the silence for a minute before continuing through. Flowey was trying hard not to be heard, but you could hear him sniffling. Hugging your arms around him and the boot, you stepped out of the Ruins.


End file.
